Fiber optic connectors are commonly employed to align and to interconnect one or more optical fibers with a variety of optical devices or with other optical fibers. For example, fiber optic connectors can be mounted on end portions of a pair of fiber optic cables, each of which include a number of optical fibers. The optical fibers of the fiber optical cables can, for example, transmit data or control signals between various remote devices, such as sensors or actuators, and a central control computer, such as a flight controller of an aircraft. The fiber optic connectors can then be interconnected such that the optical fibers of a first fiber optic cable are aligned with the optical fibers of a second fiber optic cable.
In order to efficiently transmit signals between optical fibers, the fiber optic connectors must precisely align the individual optical fibers such that the optical signals transmitted therethrough are efficiently coupled from fiber to fiber. Such alignment is particularly essential in connecting single mode optical fibers which generally have a light transmitting core of approximately 2-10 micrometers in diameter and which must be precisely aligned with the light-transmitting core of another single mode optical fiber of similar size in order to efficiently transmit optical signals therethrough.
In order to effectively couple optical signals from fiber to fiber, a fiber optic connector must maintain the precise alignment of the individual optical fibers in a predetermined manner such that the optical fibers will remain aligned as the fiber optic connector is mated with another fiber optic connector or with other types of optical device. Therefore, a variety of methods have been developed to align individual optical fibers prior to sealing the optical fibers within the fiber optic connector.
For instance, U.S. Pat. No. 5,606,635 teaches an improved fiber optic connector and associated fabrication method which includes a substrate and at least one microactuator mounted on the substrate and at least one microactuator mounted on the substrate and adapted for relative movement therewith such that an optical fiber which is mounted to the microactuator can be precisely aligned. By precisely positioning the optical fibers, such as with respective lens elements (viz., graded index lens elements), the fiber optic connector of the '635 patent efficiently couples the aligned optical fibers, such as single mode optical fibers, with other optical devices, including other optical fibers. Additionally, the microactuator used in the fiber optic connector described in the '635 patent is controllably positioned relative to the substrate so as to precisely align the optical fiber mounted thereto after the connector housing has been hermetically sealed so as to further enhance the precision with which the optical fibers can be aligned. The positioning means described in the '635 patent for the microactuators is a bimorphic actuator formed of two different materials that respond differently to electrical stimuli such that a deflection created in the bimorphic actuator by electrical stimuli can be used to controllably position a carrier body to which an optical fiber is fixed. Two or three bimorphic actuators are described as usable in the '635 patent such that the carrier holding the optical fiber can be controllably positioned in first, second or third orthogonal directions.
While the fiber optic connector of U.S. Pat. No. 5,606,635 provides a significant improvement over previous active fiber micro-aligner actuator technologies, further improvements are nonetheless desired in the fiber optic connector field. For example, fiber optic circuits and sensors that are embedded in composite structures, such as fiber-reinforced plastics (e.g., a cured prepreg of carbon fiber reinforced epoxy) are desirable over other types of sensors, e.g., surface attached-optical fibers or metallic wires or strain gages, for a number of reasons. Namely, embedded fiber optic circuits and sensors have many benefits over alternative types of sensors, such as well-tolerating the composite manufacturing process; they do not degrade the composite strength; they are EMI and EMP insensitive; they are non-magnetic and are transparent to radar; they provide increased sensitivity as compared to conventional strain gauges; the embedded optical sensors are multiplexable and, therefore, require fewer egress points; and they are relatively lightweight.
In implementation, however, the embedded fiber-to-embedded fiber coupling first requires the fiber to be egressed from the composite structure and, secondly, it requires special protection from being sheared off during the manufacturing process. Clean trimmed fiber optics eliminate this vulnerability but must allow for micron tolerances, which are too large. Previously, hand alignment of each individual fiber at the component's edge egress has been used. However, such a manual approach makes it infeasible to correct for tolerance errors in a fielded system.
As can be appreciated, inadequate fiber optic coupling has been a barrier preventing single mode and multimode fiber optic sensors systems from being incorporated into composite structures, i.e., structures having embedded fiber optics. This dilemma is driving the use of alternative sensor technologies and less desirable surface attachment processes. For instance, surface attached optical fibers are vulnerable to damage and cannot measure important strains and temperatures unlike the embedded case.
Therefore, prior to the present invention, a need has existed for an optical connector which is capable of providing optical coupling between two structurally spliced machined composite components in which there are edge egressed embedded single mode fiber optics.